1. Field of the Invention
The present invention relates to the field of combustion chambers for aviation turbine engines. More particularly, the invention relates to a combustion chamber for an aviation turbine engine, the combustion chamber being annular about a longitudinal axis A, being defined by an outer side wall, an inner side wall, and an annular chamber end wall connecting one end of the outer side wall to one end of the inner side wall, the outer side wall including, distributed along its circumference, spark plugs, primary holes, and dilution holes situated downstream from the primary holes in the direction of the longitudinal axis A.
In the description below, the terms “upstream” and “downstream” are defined relative to the normal flow direction of air through the combustion chamber. The terms “inner” and “outer” relate to the region inside and to the region outside the combustion chamber, respectively.
2. Description of the Related Art
FIG. 1 is a longitudinal section view of a sector of a combustion chamber 10 of an aviation turbine engine. The combustion chamber 10 is annular about a longitudinal axis A. It is defined by an outer side wall 12 that is substantially cylindrical about the axis A, by an inner side wall 14 that is substantially cylindrical about the axis A and of mean diameter less than the mean diameter of the outer side wall 12, and by an annular chamber end wall 13 that connects one end of the outer side wall 12 to the facing end of the inner side wall 14 so as to close the upstream end of the combustion chamber 10. Thus, the mean surface passing through the combustion chamber 10 from the chamber end wall 13 to the downstream end 15 is a cone about the longitudinal axis A. The line of intersection between this cone and a plane containing the longitudinal axis A is referenced C in FIG. 1.
The chamber end wall 13 has a plurality of fuel injector systems 33 that inject fuel into the combustion chamber 10. The injector systems 33 are distributed around the longitudinal axis A.
Air penetrates into the combustion chamber 10 via the chamber end wall 13, via primary holes 100, via dilution holes 200, and via cooling holes (not shown), all of these holes being in the outer side wall 12, and also via primary holes 110, dilution holes 210, and cooling holes (not shown), all of these holes being in the inner side wall 14.
Spark plugs 36 (visible in FIG. 4) are situated substantially level with the primary holes 100 and they are distributed regularly around the outer side wall 12 about the longitudinal axis A.
In the configuration shown in FIG. 1, the combustion chamber 10 has two spark plugs 36 (see FIG. 4), which are thus diametrically opposite about the axis A.
Such a combustion chamber is designed to operate at a variety of altitudes. Present standards require combustion chambers to be suitable for operating at altitudes that are ever higher. In particular, in the event of combustion being interrupted, a combustion chamber must be capable of being re-ignited at the highest possible altitude, referred to as the re-ignition ceiling.
High altitude re-ignition tests on combustion chambers have shown that in order to increase the re-ignition ceiling, and thus the ability of a combustion chamber to re-ignite at a higher altitude, it is necessary:                either to reduce the percentage of air that is introduced into the combustion chamber via the primary holes (relative to the total quantity of air passing through the combustion chamber);        or else to increase the volume VZP of the primary zone so that air is distributed in constant manner within the combustion chamber (i.e. the distribution of air between the various air inlets into the combustion chamber is constant). The primary zone is defined as the region of the combustion chamber that extends between the chamber end wall and the plane containing the primary holes.        
Both of those solutions suffer from the drawbacks of giving rise to an increase in the level of smoke and in the level of NOx emitted by the combustion chamber.
In present combustion chambers, obtaining a higher re-ignition ceiling thus runs the risk of no longer being capable of satisfying pollution standards, particularly since these standards are becoming ever more severe.